Mike Nichols told the same story about the song in one of his final interviews. Simon's original subject for the song was Eleanor Roosevelt ("And here's to you, Mrs. Roosevelt...") so he didn't think it would work in the movie. But as soon as Nichols heard the only completed stanza he insisted that they change the name to Robinson and use it in the movie. The reason you hear it over and over again in the film as a guitar riff without lyrics is indeed because Simon had only written one verse.